The electrical characteristics of the discharge path of an open gas discharge tube mainly depend on environmental parameters, so the stability of the operation cannot be guaranteed. In order to improve the working stability of the gas discharge tube, the gas discharge tube mostly uses metallized ceramic insulator and electrode welding technology, so as to ensure the sealing of the shell and the discharge gap of the air tightness, which creates conditions for the selection of gas types and pressure in the discharge tube, the gas discharge tube is generally charged with neon or hydrogen gas.

The various electrical characteristics of the gas discharge tube, such as DC breakdown voltage, impulse breakdown voltage, impulse current resistance, power frequency current resistance and service life, can be adjusted and optimized according to the requirements of the system. This adjustment is often achieved by changing the type of gas in the discharge tube, the pressure, the composition of the electrode coating material and the distance between the electrodes.

There are two types of gas discharge tube and three electrode discharge tube. Some gas discharge tubes have electrode leads, while others have no electrode leads.

In terms of structure, the gas discharge tube can be regarded as a symmetrical switch with a small capacitance, which is turned off under normal working conditions, and its inter-electrode resistance is above megohm level. When the surge voltage exceeds the voltage strength of the circuit system, the gas discharge tube is broken down and arc discharge occurs, because the arc current is low, only tens of volts, which can limit the further rise of the surge voltage in a short time. The gas discharge tube uses the above principle to limit the surge voltage and to protect the circuit from overvoltage.

As the overvoltage decreases, the current through the gas discharge tube also decreases. When the current falls below the minimum current value required to maintain the arc state, the arc discharge stops and the glow of the discharge tube is extinguished.

The gas discharge tube is mainly used to protect the safe operation of communication systems, traffic signal systems, computer data systems, and external cables of various electronic equipment and electronic instruments. The gas discharge tube is also the circuit protection element against lightning strike and instantaneous overvoltage.

The gas discharge tube has the characteristics of large current carrying capacity, fast response time, small capacitance, small volume, low cost, stable performance and long life. The disadvantage is that the ignition voltage is high, the cut-off state can not be restored under DC voltage, and it can not be used to protect low-voltage circuits, and the performance will decline after each transient voltage action.